The prior art proposed packaging machines of products inside a plastic film equipped with a “L”-shaped welding frame with two bars for welding and cutting the film, that are respectively transverse and longitudinal with respect to the plastic film supplying direction and are mutually integral, like the one shown in enclosed FIG. 1 and described below. Such machines have the problem that, in order to guarantee the perfect contact between the welding and cutting bars and their abutments, this allowing the complete cutting and welding of the plastic film, particularly accurate assemblings and setting ups are necessary.
Other automatic packaging machines existing on the market are called continuous head welding machines. They are different from the other machines with cutting and welding bars with frame linked as an “L” since they are equipped with a welding and cutting head arranged on the longitudinal side with respect to film sliding. This head is usually composed of hot rollers that cut and weld the plastic film, or of small hot blades, also placed as a pair of scissors. These systems are very complicate and costly for their setting up, and do not provide any guarantee of continuity and good operation during long operating cycles. This is partly due to the residual dirt of the plastic film that carbonizes on the hot welding blades.